I realize that everyone is different. I am a 49 year old casual runner. I have been running since April. I just got back into it after about a decade off. I am not training for a race. I am just trying to stay fit and have fun. I run 3-4 times a week. Usually length is 3-4 miles. My mile times are usually between 9-10 minutes. The way my life is right now I have trouble finding more than 3-4 days a week to run. I was just wondering if I am not running long enough. Years ago my short runs were 5 miles. So, I was wondering if a 30-40 minute run is enough to stay fit? Or should I try and extend my runs to closer to an hour? I guess my question is are there any runners that really only run 3 miles at a time.